I'm following the

And my Firestore database:

CodePudding user response：

I think the issue here is related to TypeScript. I believe best-practice, in this case, would be for you to use the private access modifier in front of firestore: Firestore while injecting it into the constructor of the component or service where you are using it, in your case app.component.ts.

The private access modifier does a couple things:

1. It makes the property a member of the class (similar to if you had declared the property in you class firestore: any;)
2. It makes the property 'private', only available in the class but not available in the template (during development - not enforced in production).

constructor(private firestore: AngularFirestore) {
  this.items = firestore.collection('items').valueChanges();
}